Safety brake



Aug. 4, 1931. A. H. WILSON 1,816,884

SAFETY BRAKE Filed Hay 1l, 1929 Patented Aug. 4, 1931 f ,UiNl'grfEre fst'fmrns PATENT OFFICE ALEXANDER II. WILSON, OI OAK PARK, ILLINOIS, A.ssIeNcR To THOMAS ELEVATOR .'OOMPANY, OF'cIIIceeo, ILLINOIS, A CORPORATION or ILLINOIS Y o j SAFETY BRAKE :Application filed May 11,

n@ Vices are particularly usefulLinconnection with`v` hoistingsapparatus k,of Various sorts, to

preventidamage andfpossible injury from the lsudden dropping o f ,a loaded cage or yother form of elevator thatvis hoisted .through the l y15 agency.ofashaft-orother rotating member nturningalways inone direction but ,they yare L,also nseful :inothersituationsiwhere it is de- ,.sirableto prevent backwardturningof arotating member under load.

' 20 f :The-main object ,O-fthepresent invention `,is

to provide a f simple, inexpensive, 1 quick actingand .highlyfeilicient automatic safety de-` f lVficeain thegeneral nature "Ofa non-reversible brake or clutch 4for the .uses .and @applications A :above indicated. ,Another fobfjectisato prowide anautomatic safetybrakeofthecharac- --ften indicated wherein the .principalbrakeelezinents shalllbe capable-of nice adjustment to insure perfect cooperation and to compen- 4-'30"Sate,forwear. f Afurtlier object is .,toprovide Y vam Iautomatic safety, )brake .whereinthe r:power ofthebrake will .be increased in iproportion to rthe. load lagainst whichrtheb,rake works.

. l,L Still further` Objectsgandfiattendant advan-4 35' l.tages .oftheinventien .willfbe apparent Ato. per- 1 sons sigillo-,din Atheart,.as;.the same, becomes better understood by reference tothe followingdescription, taken `in connection. ,with the (accompanying, ,drawings .in which I have ili yflustratedVVA A,one practical Vfand approved ,em-

bodiment of ,the invention-and wherein- 'Fig 1' is an elevation'of the device with the front coyer of the pivoted brake Shoe holder removed.; f

1929. serial No. l362,200.

2-2 of Fig. 1,'looling downwardly and with the cover in place.

Referring to the drawings, I1() designates a shaft which may be assumcdto Vrotate lalways inthe direction indicated by the'arrow 'when under load7 and accidental.backward turning of which, under the pull of the load, my improved-safetybrake or clutch is designed to prevent. Keyed on one end Of this shaft is a brake drum 11. yllncircling the drum 11 is a brake shoe holder comprisingl` in the-instance showma shallow cup-shaped body 12 anda detachable cover plate 13. :The body 12 `also yencircles the shaft, with clearance as show-nin Fig. 2, to permit a Ytilting movement of the brake shoe holder'as hereinafter described. The'brale shoe holder is pivotally supported Ona pivot Apin 14 which may be mounted in the upper partof a. pedestal 15 restingon thcfioor or a suitable platform 16 and projecting into the holder through an opening 17 in the 'rim of the latter; the ends y ofthe pin entering holes in a pair of webs 18 cast in the holder bedr/12. It will be noted that the opening 17 is wider than the portion yof thepedestal occupying the same, to permit alimited tilting movement ofthe holder hereinafter described.

In one side of the holder is cast a rib 19 having a transyersehole 2() in which rib is yfitted Va brake'shoe stem orshank 21 vherein show-n as a short'threadcd rod7 On the inner -end of which is pivoted at 22 a brake shoe A22. vThe stem 21 'is adjustable endwise in the hole-20. and is locked in adjusted position yby nuts A2f-hand 24e, whereby the shoe can be nicely adjusted for proper engagement with the brake drum.

At 4ai diametrically yOpposite point in the Aholder 12,there isrmounted inland between a pair of cast webs 251a pivot pin-26 that supports-the outer end `of an upwardly-and inwardly inclined togglefxlink 27. On the inner ,free end of link 27 is pivotally mounted at 28 lbrake .shoe 29 thatseats .on the periphery f for purposes of illustration one practical me! of the drum. It will be observed that the pivot 28 lies above a line drawn between the aXis of the drum and the pivot 26, so that the link 27 and rshoe 29 form the two arms of a toggle which tends to straighten under the friction of the drum on shoe 29 when the drum starts to rotate backwardly'or in a clockwise direction viewing Fig. l; the normal or forward direction of the drum being counter-clockwise, as shown by the arrow.V

It will be observed that the pivot 14 of the brake shoe `holder lies below the axisl of the drum and to one side of a vertical line passing through the center of gravity of the holder, so that the latterv tends to tilt by gravity toward the left, viewing Fig. l, or in the forward turning direction of the drum and its shaft; and the gravity tilting movement is limited by a suitable stop which is preferably adjustable, such as the threaded pin 30 entering atapped boss 31 in thelower side of the rim of the holder and rest-ing at its lower end on the floor or platform 16.

The operation will be readily apparent from the foregoing description. So long as the shaft and drum arek turning in the normal forward-working direction indicated by the arrows,'both brake shoes ride idly over the periphery of the drum. The instant the shaft and drumstart to turn in the opposite vor j backward direction, the friction oft-he drum on shoe .29` tends to 'straighten the toggle, and this forces link 27V outwardly, tilting the brake shoe holder to the right, viewing Fig. l, and 'thisjams brake shoe 22 hard against vthe drum, arresting further tilting movement of theholder and so causing `both shoes to tightly grip and clamp the drum, and the heavier the load, the harder will be thej amming action of the shoes on the drum. Subsequent rotation of the drum and shaft in 'k normal forward direction breaks the toggle, f permitting vthe holder to tilt back to the normal positionshown in Fig l until arrested against the rim of the holder, l provide a web 32 between the webs 425, which acts as a stop for-the heel of link 27 Whilel have herein in shown and described chanical form of the invention, l. do not limit the latter to the details of structureand arp 'said drum 'and to one sideLof a vertical v`line (passing through the centerof gravity of "Y i165 said holder, said holder having portions by stop et). To prevent the possibility of shoe 29 and its ylink 27 being thrownbackwardly rangement shown and described, but reserve all such variations and modications as fall n l. In an automatic safety brake of the type described,- the combination with a horizontally rotating brake, drumfof a Ybrake shoe -holder'pivotally mounted belowv the airis' lying on opposite sides of said drum, a pair of brake shoes so mounted on said oppositely lying portions of the holder as to ride idly on said drum when the latter is rotating in 'the direction in whichsaid holder tendsto tilt by gravity, and to grip said drum under the friction of the latter on one of said shoes where the drum rotates in the opposite direction, and a stop limiting the gravity tilting; movement of said holder.

2. In an automatic safety brake of the type described, the combination with a horizontally rotating brake drum, of a brake shoe-holder pivotally mounted below the axis of said drum and toone side of a vertical line passing through the center of gravityof said holder, said holder having portions lying on opposite sides of said drum, a brake shoe mounted on one of saidoppositely lying portions of the holder and movablel under a tilting movement of the latter into braking engagement with said-drum, a'link pivoted on the other oppositelyV lying portion of the holder, a brake shoe mounted on the free end of said link, said last-named brake shoe and its link forming a toggle whichl tends to straighten under the friction of the drum when the latter rotates in a backward direction, and a stop limiting the'gravity tilting movement of said holden v Y v3. In an automatic safety brake of the type described, the combination with a hori- Zontally rotating brake drum, of` a brake shoe holder Vencircling said drum and pivotally mounted below the aXis of the` latterY and to one side of aV vertical line passing through the'center of gravity of said holder,

an endwise adjustable brake shoeIV Vstem mountedon one side of said holder, a-brake kshoe pivoted on the inner end ofv said stem,

a link pivoted on the opposite sideof said holder, a brake shoe pivoted on the inner end of said link, said last-mentioned brake shoe and its link forming a toggle which tends to straighten and tilts said holder against gravity wherethe vdrum rotatesv ina backward direction, and an adjustable vstop limiting" the gravity-tilting movement of said holder. i'

4. In' an automatic described, the combination with a rotatable Vshaft and a brake drum fast thereon, of a rigid brake shoelholder mounted eccentrically of the aXis of said drum on a single pivot and encirclingsaid shaft with clearance,and

a pair ofbrake shoes'mounted "on said holder on opposite sides of said shaft, .said' brake shoes being so mounted as to ride idly on said drumy when the latterY rotates in 'one direction and to grip said drum under a tiltingmovement of said holder when, the drum rotates inthe other directioni, o 1

5; In an automatic safety brake ofthe type described, Y the combination with a rotatable shaft and a brakeA drum fast thereon, Vof a safety brake of the type' and a brake shoe pivotally mounted on the free end of said link7 said last-named brake 'shoe and its link forming a toggle which straightens and tilts said holder thereby carrying said *irstnamed brake shoe into engagement With said drum when the latter rotates in a backward direction.

Y kALEXANDER H. WILSON. 

